Method of positioning patterns from block copolymer self-assembly

ABSTRACT

A method of controlling both alignment and registration (lateral position) of lamellae formed from self-assembly of block copolymers, the method comprising the steps of obtaining a substrate having an energetically neutral surface layer comprising a first topographic “phase pinning” pattern and a second topographic “guiding” pattern; obtaining a self-assembling di-block copolymer; coating the self-assembling di-block copolymer on the energetically neutral surface to obtain a coated substrate; and annealing the coated substrate to obtain micro-domains of the di-block copolymer.

BACKGROUND OF THE INVENTION

The present invention relates generally to the fabrication of integratedcircuits and, more particularly, relates to the fabrication ofintegrated circuits by a patterning process which uses self-assemblingpolymers.

The semiconductor industry has a need to manufacture integrated circuits(ICs) with higher and higher densities of devices on a smaller chip areato achieve greater functionality and to reduce manufacturing costs. Thisdesire for large-scale integration has led to a continued shrinking ofthe circuit dimensions and features of the devices.

The ability to reduce the sizes of structures such as gates in fieldeffect transistors (FETs), is driven by lithographic technology whichis, in turn, dependent upon the wavelength of light used to expose thephotoresist. In current commercial fabrication processes, opticaldevices expose the photoresist using light having a wavelength of 193 nm(nanometers). Research and development laboratories are experimentingwith the EUV (13 nm) wavelength to reduce the size of structures.Further, advanced lithographic technologies are being developed thatutilize immersion techniques to improve resolution.

A challenge facing lithographic technology is fabricating featureshaving a critical dimension (CD) below 50 nm. All steps of thephotolithographic techniques currently employed must be improved toachieve the further reduction in feature size.

In a conventional lithography technique, light is exposed through abinary mask to a photoresist layer on a layer of material. Thephotoresist layer may be either a positive or a negative photoresist andcan be a silicon-containing, dry-developed resist. In the case of apositive photoresist, the light causes a photochemical reaction in thephotoresist. The photoresist is removable with a developer solution atthe portions of the photoresist that are exposed through the mask. Thephotoresist is developed to clear away these portions, whereby aphotoresist feature remains on the layer of material. An integratedcircuit feature, such as a gate, via, or interconnect, is then etchedinto the layer of material, and the remaining photoresist is removed.

The line-width of the integrated circuit feature is limited using theconventional lithography process. For example, aberrations, focus, andproximity effects in the use of light limit the ability to fabricatefeatures having reduced linewidth. Using a 248 nm wavelength lightsource, the minimum printed feature linewidth is between 300 and 150 nm,using conventional techniques. The most advanced lithography tools cannow resolve to 100 nm feature size which can be improved to 70 to 80 nmwith immersion lithography. With IC design expected to require sub-50 nminterconnects, it is apparent that conventional lithography cannot meetthis design requirement.

Accordingly there is a need for reducing the IC interconnect openingdiameter to below the resolutions of the conventional lithographictools, to improve circuit layout density.

SUMMARY OF THE INVENTION

It has been known that certain materials are capable of organizing intoordered patterns under certain desired conditions, which is typicallyreferred to as the self-assembly of materials.

The present invention relates to a method of controlling the lateralposition of lamellar lines in a trough pattern having energeticallyneutral bottom and sides by the introduction of two levels oftopographic patterns on a substrate. Control of both alignment andlateral position of the lamellae is obtained.

In the method, two levels or layers of topographic patterns are formedon a suitable substrate. Preferably, both levels (layers) of topographicpatterns are prepared from a photosetting polymer, which can be the sameor different for each level. An example of a suitable substrate is asilicon wafer having a thin layer of silicon dioxide disposed thereupon.Of the two levels or layers formed on the substrate, the layer closestto the substrate (first topographic pattern) is preferably formed last.The first topographic “phase pinning” pattern is formed by cutting awaya part of the surface of the second topographic “guiding” pattern afterthe second topographic “guiding” pattern is formed on the suitablesubstrate. In an alternative embodiment, the first topographic “phasepinning” pattern is formed before the second topographic pattern.

The first topographic “phase pinning” pattern is formed so as to containa mesa having an edge. Alternatively, the first topographic “phasepinning” pattern can be in the shape of a ledge, wherein the ledgecomprises an overhang. The surface comprising both the first topographic“phase pinning” pattern and the second topographic “guiding” pattern isthen made energetically neutral by methods known to one of ordinaryskill in the art. An energetically neutral surface, which includes atleast the sidewalls and the bottom of the trench patterns, provides forthe later formation of lamellar micro-domains from a self assemblingdi-block copolymer. The lamellar micro-domains, which have alternatingblocks of different compositions, are substantially perpendicular to thesidewalls of the trench patterns.

The layer further removed from the substrate is a second topographic“guiding” pattern. The second topographic “guiding” pattern residessubstantially on top of the first topographic pattern, thus forming acomposite comprising substrate/first topographic pattern/secondtopographic pattern. The second topographic pattern comprises at leastone trough. The at least one trough can have a shape of a line, an arc,an angle, a combination thereof or the like. The at least one troughcontains at least one open end. Thus, the at least one trough cannot becompletely closed off like a box structure. Preferably, the at least onetrough contains an opening at both ends of the trough; that is, thetrough is open at both ends. Open end(s) of the at least one trough arepositioned close enough to the first topographic “phase pinning” patternso that one block of a di-block copolymer can be pinned to the edge.This allows positioning the starting point of line-forming lamellarmicro-domains in the trough. The lateral position (registration) of thelamellae is thus controlled.

After formation of first and second topographic patterns, and alsomaking the surfaces of said topographic patterns energetically neutral,a solution or dispersion, comprising a block copolymer, or a blend oftwo or more block copolymers, and a solvent such as toluene, is spuncast onto the composite comprising substrate/first topographicpattern/second topographic pattern. One block of the di-block copolymeris “pinned” to the edge of the mesa. This “pinning” action controls theregistration (lateral position) of the lamellae in the trough.

It is theorized that the block that is more likely to bend has atendency to “curve around” the edge, or the ledge, of the mesa, thussubstantially “pinning” the self-assembling di-block copolymer. In thecase of PS-b-PMMA, the styrene block cannot bend as readily as themethylmethacrylate block; and thus the methylmethacrylate block is“pinned” by the edge of the mesa. The spun cast di-block copolymer,preferably PS-b-PMMA, is then annealed to obtain equilibrium morphology.An etching step can then be performed on the assembly of lamellae toobtain a line/space array. The line/space array, which is formedperpendicular to the sidewalls of the trench, has a sublithographicdimension.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a first topographic laminatethat comprises a substrate, a first topographic pattern that acts as aphase pinning pattern, and a second topographic pattern that acts as aguiding pattern.

FIG. 2 is a schematic representation of a second topographic laminatethat comprises a substrate, a first topographic pattern that acts as aphase pinning pattern, a second topographic pattern that acts as aguiding pattern, and a pinned di-block copolymer that has assembled intolamellar micro-domains.

FIG. 3 is a schematic representation of a third topographic laminatethat comprises a substrate, a first topographic pattern that acts as aphase pinning pattern, a second topographic pattern that acts as aguiding pattern, and a di-block copolymer that has one of themicro-domains removed.

FIG. 4 is a plan-view scanning electron microscope (SEM) micrograph oflamellar micro-domains of a polystyrene-b-polymethylmethacrylate(PS-b-PMMA) di-block copolymer wherein the alignment and theregistration of the lamellar micro-domains are controlled by thetopographic laminate.

DETAILED DESCRIPTION OF THE INVENTION

A monomer as used herein is a molecule that can undergo polymerizationthereby contributing constitutional units to the essential structure ofa macromolecule, an oligomer, a block, a chain and the like.

A polymer as used herein is a macromolecule comprising multiplerepeating smaller units or molecules (monomers) bonded togethercovalently. The polymer may be a natural polymer or a semi-syntheticpolymer or a fully synthetic polymer.

A copolymer as used herein is a polymer derived from more than onechemical species of smaller unit or monomer.

A block copolymer as used herein is a copolymer that comprises more thanone species of monomer, wherein the monomers are present in homogenouslarger units or blocks. Each block of the specific monomer comprisesrepeating sequences of only that monomer, uninterrupted by othermonomers. A formula (1) representative of a block copolymer is shownbelow:—(A)_(a)—(B)_(b)—(C)_(c)—(D)_(d)—  (1)wherein A, B, C and D represent different monomer units and thesubscripts “a”, “b”, “c” and “d” represent the number of repeating unitsof A, B, C and D respectively. The above referenced representativeformula is not meant to limit the structure of the block copolymer usedin an embodiment of the present invention. The aforementioned monomersof the copolymer may be used individually and in combinations thereof inaccordance with the method of the present invention.

A di-block copolymer has blocks of two different polymers. A formula (2)representative of a di-block copolymer is shown below:—(A)_(m-)(B)_(n)—  (2)where subscripts “m” and “n” represent the number of repeating units ofA and B, respectively. The notation for a di-block copolymer may beabbreviated as A-b-B, where A represents the polymer of the first block,B represents the polymer of the second block, and -b- denotes that it isa di-block copolymer of blocks A and B. For example, PS-b-PEO representsa di-block copolymer of polystyrene (PS) and poly(ethylene oxide) (PEO).

A crosslinkable polymer as used herein is a polymer having a smallregion in the polymer from which at least one polymer chain may emanate,and may be formed by reactions involving sites or groups on existingpolymers or may be formed by interactions between existing polymers. Thesmall region may be an atom, a group of atoms, or a number of branchpoints connected by bonds, groups of atoms or polymer chains.

Typically, a crosslink is a covalent structure, but the term is alsoused to describe sites of weaker chemical interactions, portions ofcrystallites and even physical interactions such as hydrogen bonding,phase separation and entanglements.

Morphology as used herein describes a form, a shape, a structure and thelike of a substance, a material and the like as well as other physicaland chemical properties (eg., Young's Modulus, dielectric constant, etc.as described infra).

Amphiphilic as used herein is used to describe a molecule and amacromolecule that is or has in part both polar and non-polar portionsthat constitute the molecule and the macromolecule.

Thermosetting polymer as used herein is a polymer or a prepolymer in asoft solid or viscous state that changes irreversibly into an infusible,insoluble polymer network by curing. Typically, curing can be by theaction of heat or radiation causing the production of heat, or both.Further, curing can be by the action of heat and/or radiation thatproduces heat resulting in the generation of a catalyst which serves toinitiate crosslinking in the region of exposure.

Photosetting polymer as used herein is a polymer or a prepolymer in asoft solid or viscous state that changes irreversibly into an infusible,insoluble polymer network by curing. Typically, curing can be by theaction of exposing the polymer or prepolymer to light (UV, IR, visible,etc.). Further, curing can be by the action of exposure to radiationresulting in the generation of a catalyst which serves to initiatecrosslinking in the region of the exposure.

Nanostructure as used herein is a structure on the order of 1 nanometer(nm) to 100 nm in dimension. Examples of the structure may include, butare not limited to, nanorods, nanosheets, nanospheres, nanocylinders,nanocubes, nanoparticles, nanograins, nanofilaments, nanolamellae andthe like, having solid composition and minimal structural dimension in arange from about 1 nm to about 100 nm. Further examples of the structuremay include but are not limited to spherical nanopores, cylindricalnanopores, nanotrenches, nanotunnels, nanovoids and the like, havingther void or shape defined by the material or matrix that surrounds themand having a diameter in a range from about 1 nm to about 100 nm.

A substrate as used herein is a physical body (eg., a layer or alaminate, a material and the like) onto which a polymer or polymericmaterial may be deposited or adhered. A substrate may include materialsof the Group I, II, III and IV elements. It may also include plasticmaterial, silicon dioxide, glass, fused silica, mica, ceramic, metalsdeposited on the aforementioned substrates, combinations thereof and thelike.

An energetically neutral surface layer as used herein is a surface layerwhose chemical and morphological composition affords substantially nopreferential or selective affinity for either polymer block in a blockcopolymer or an associated functional group or moiety, such as throughionic bonds, dipole-dipole forces, hydrogen bonding and similarintermolecular forces.

A mesa as used herein is an isolated plateau or hill having abrupt orsteeply sloping sides and a level top. A mesa as used herein can also bea broad terrace with an abrupt slope or escarpment on one side.

A trough as used herein is a structural depression that is long andnarrow or shallow. The structural depression such as a canal or channelhas a bottom or floor which is substantially horizontal; and has twoopposing sides, the sides being substantially parallel to one anotherand being separated from one another by a distance that is substantiallythe distance of the width of the canal or channel. The two opposingsides are substantially perpendicular to the bottom or floor of thecanal or channel.

A lamellar micro-domain as used herein is topographic structure ofalternating rows or columns of a block copolymer having at least twodifferent polymeric blocks.

A lamellar micro-domain period (P) as used herein is the distancebetween two adjacent lamellar micro-domains.

An edge as used herein is that linear or curved part of a mesa that isbetween the steeply sloping side of the mesa and the level top of themesa.

A ledge as used herein is a type of mesa that has an edge which is inthe shape of a “springboard”, that is, the ledge has a thin section thatjuts out from the rest of the mesa to form an overhang.

Alignment is a forming in line of elements, each element having acorrect relative position. Alignment as used herein is the position ofthe self-assembled micro-domains in the trough with respect to the sidesof the trough.

Registration is a bringing together of two things where there iscomplete agreement with respect to position. Registration as used hereinis the position of the self-assembled micro-domains in the trough withrespect to the end (or ends) of the trough.

Self-assembling polymers are capable of self-organizing intonanometer-scale patterns, enabling future advances in semiconductortechnology as shown for example in Nealey et al., “Self-assemblingresists for nanolithography” Electron Devices Meeting. 2005. IEDMTechnical Digest. IEEE International 5-7 Dec. 2005 Page(s):4 pp. Asdescribed in this reference, each self-assembling polymer systemtypically contains two or more different polymeric block components thatare immiscible with one another. Under suitable conditions, the two ormore immiscible polymeric block components separate into two or moredifferent phases on a nanometer scale and thereby form ordered patternsof isolated nano-sized structural units. U.S. Patent ApplicationPublication 2005/0167838 discloses the use of a self-assembled polymerpattern to form sub-lithographic features in an oxide.

The block copolymers as mentioned hereinabove preferably comprise A:Bblock copolymers wherein A is a first polymeric component and B is asecond polymeric component having a weight ratio of A:B from about 20:80to about 80:20. The single unit polymer block preferably comprisescylindrical or lamellar micro-domains. The block copolymer may be anorganic block copolymer. In the A-b-B scenario, specific examples of theA block are (but not limited to): poly(ethylene oxide), poly(ethyleneglycol), poly(propylene glycol), poly(alkylene oxides), poly(acrylicacids), poly(methacrylic acids), poly(dimethylaminoethylmethacrylate),poly(hydroxyalkylmethacrylates), poly(alkylene oxidemethacrylates),poly(hydroxystyrene), carbohydrate polymers, poly(vinylalcohols),poly(ethylene imines), polyoxazolines, polypeptides,poly(vinylpyridines), polyacrylamides, poly(methylvinylethers),poly(vinylcarboxylic acid amides), poly(N,N-dimethylacrylamides) and thelike. Specific examples of the B block are (but not limited to)polystyrene, poly(alpha-methyl styrene), polynorbornene, polylactones,polylactides, polybutadiene, polyisoprene, polyolefins,polymethacrylates, polysiloxanes, poly(alkyl acrylates), poly(alkylmethacrylates), polyacrylonitriles, polycarbonates, poly(vinylacetates),poly(vinylcarbonates), polyisobutylenes and the like. The blockcopolymers can be readily selected from the group consisting ofpolystyrene-block-polymethylmethacrylate (PS-b-PMMA),polystyrene-block-polyisoprene (PS-b-PI),polystyrene-block-polybutadiene (PS-b-PBD),polystyrene-block-polyvinylpyridine (PS-b-PVP),polystyrene-block-polyethyleneoxide (PS-b-PEO),polystyrene-block-polyethylene (PS-b-PE),polystyrene-b-polyorganosilicate (PS-b-POS),polystyrene-block-polyferrocenyldimethylsilane (PS-b-PFS),polyethyleneoxide-block-polyisoprene (PEO-b-PI),polyethyleneoxide-block-polybutadiene (PEO-b-PBD),polyethyleneoxide-block-polymethylmethacrylate (PEO-b-PMMA),polyethyleneoxide-block-polyethylethylene (PEO-b-PEE),polybutadiene-block-polyvinylpyridine (PBD-b-PVP), andpolyisoprene-block-polymethylmethacrylate (PI-b-PMMA). In a particularlypreferred, but not necessary, embodiment of the present invention, theblock copolymers comprise PS-b-PMMA.

An energetically neutral surface can induce the lamellae-forming blockcopolymer to align perpendicularly with respect to the sidewalls of thetrough that is formed as part of the second topographic pattern. Thisalignment is achieved because lamellae of the polymer blocks A and B ofthe di-block copolymer can self-assemble, being induced to alignperpendicular to the sidewalls of the trough pattern. The same alignmentprinciple can be applied to formation of line-forming morphology withrespect to parallel cylinders. As an example, for a trough withenergetically neutral sidewalls and a preferentially wetted substrate,cylinder forming block copolymers may be used to generate linessubstantially normal to the trough sidewalls.

Rod-coil block copolymers such as poly(hexyl-isocyanate)-b-polystyreneand poly(phenyl-quinoline)-b-polystyrene can be used to form filmswherein the high stiffness of one of the domains of such blockcopolymers induces alignment of line-forming structures substantiallynormal to the sidewalls of the trough.

Rigidity of a particular polymer block in the di-block copolymer can becontrolled by combining the di-block copolymer with a third, misciblematerial. The third material is miscible with the particular block ofthe di-block copolymer. The miscible material can act as a stiffeningcompound, increasing the rigidity of that particular block of thedi-block copolymer. If the miscible material is crosslinkable, then thestructure formed by the alignment of the line-forming microdomains canbe made substantially permanent as by crosslinking.

After the film of lamellar micro-domains is formed, at least onemicro-domain can be removed from the film to obtain an orientedstructure comprising a line/space array. Removal of the micro-domain canbe obtained by various methods known to one of ordinary skill in theart. Such methods are thermolysis, UV/ozone processing, supercriticalCO₂ processing, solvent extraction, dry etching, reactive ion etching(RIE), wet etching and the like. Processes can also be employed incombination. Removing at least one micro-domain can comprise removing atleast one domain from one or more polymer blocks of the di-blockcopolymer. In one example, in the case of di-block copolymers, removalof only the first block, only the second block, or both first and secondblocks can be employed.

If a miscible material is employed in one block of the di-blockcopolymer, then both blocks can be removed, leaving the misciblematerial in the at least one trough. The miscible material in the troughforms an oriented structure. Preferably, the oriented structure is ananostructure.

An example of employing a miscible material is usingpolymethylsilsesquioxane (PMSSQ). The PMSSQ can be mixed with a di-blockcopolymer of polystyrene and poly(ethyleneoxide) (PS-b-PEO). In apreferred embodiment, the molecular weight of the PS block is about19,000 grams/mole (g/mol); and the molecular weight of the PEO block isabout 12,000 grams/mole. The composition of the PS-b-PEO can vary in theamount of PS block and PEO block present in the di-block copolymer. Themolecular weight of each block of the di-block copolymer can be in arange from about 2,000 g/mol to about 100,000 g/mol. The total molecularweight of the di-block copolymers can range from about 10,000 to about200,000 g/mol. The fraction of monomer blocks present can be representedin percent millimoles (% mmol), percent by weight (wt %), volumefraction or the like. The combined volumetric fraction of the PEO (withmiscible PMSSQ) block present in the di-block copolymer is preferablyabout 0.65. The PMSSQ is preferentially miscible with the PEO block ofthe PS-b-PEO over the PS block. The PMSSQ can act as a stiffening agentto increase the rigidity of the PEO block both in the di-block copolymerand in the PEO micro-domains in the formed film that is present in thetrough.

The trough can be prepared using electron beam (e-beam) lithography.Alternatively, other processes such as chemical vapor deposition (CVD),plasma deposition, stereolithography, photolithography, sputtering,nanoimprinting and the like can be employed to create the at least onetrough in the second topographic pattern. It is necessary that any openend of the trough be positioned relatively close to the edge of the mesaor ledge found in the first topographic pattern. The distance between anopen end of the trough and the edge of the mesa can be expressed interms of a lamellar domain period (P). The lamellar domain period (P) ofa di-block copolymer that can form micro-domains can be defined as thedistance between two adjacent micro-domains. The distance between theopen end of a trough found in the second topographic pattern and theedge of a mesa found in the first topographic pattern is, in a preferredembodiment, about 0.5P to about 1.0P, whereby the at least one edge actsto pin one block of the di-block copolymer. Preferably, the width of thetrough is about 100 nanometers to about 500 nanometers. More preferably,the width of the trough is about 200 nanometers to about 400 nanometers.Most preferably, the width of the trough is about 300 nanometers.

A trough in the second topographic pattern can be made energeticallyneutral by deposition of a thin film of appropriate chemicalcomposition. The process of making the surfaces energetically neutralcan be any process known to one of ordinary skill in the art. One methodof making the topographic surface neutral to both blocks of a di-blockcopolymer is by forming a random copolymer brush coating on the surface.If the di-block copolymer is a PS-b-PMMA copolymer, then a random brushcopolymer of PS-PMMA is anchored to the surface of the pre-patternedtopographic surface. Other methods of making the topographic surfacesneutral to both blocks of the di-block copolymer are: coating withself-assembled mono-layers, coating with thermally crosslinkable polymerfilms, and coating with photochemically crosslinkable polymer films. Theentire surface of the substrate containing both topographic patterns canbe made energetically neutral. At the very least, both sidewalls of thetrench and the bottom of the trench must be made energetically neutral.

The formation of self-assembled structures (nanostructures) ofline-forming micro-domains can be accomplished by forming a film on anenergetically neutral substrate by a process selected from the groupconsisting of spin casting, dip coating, spray coating, thermalannealing, vapor annealing, combinations thereof and the like. Examplesof line-forming micro-domains are lamellar micro-domains and cylindricalmicro-domains.

After the surface of the substrate is made energetically neutral, a selfassembling di-block copolymer is coated onto the surface of thesubstrate to obtain a coated substrate. The coated substrate is thenheated, as by an annealing step, to a temperature that is below themelting point temperature of the di-block copolymer. A self assembleddi-block copolymer having lamellar microdomains within the trough isobtained.

The present invention relates to a method for preparing a patternconsisting essentially of an array of substantially parallel lines fromself-assembly of polymeric micro-domains. The array of lines has asub-lithographic dimension. The process comprises a first step ofproviding a substrate having an energetically neutral surface layer. Theenergetically neutral surface layer comprises at least one mesaintegrally disposed thereon, and at least one trough integrally disposedthereon. The mesa has at least one edge. The at least one troughcomprises a bottom surface, a substantially planar first sidewall and asubstantially planar second sidewall opposite the first sidewall. Thefirst sidewall and the second sidewall are substantially normal to thesurface layer. The first and second sidewalls are separated by adistance corresponding to the width of the bottom surface of the trough.The at least one trough has at least one open end. The process comprisesa second step of providing a linear substantially symmetrical A-b-Bdi-block copolymer. The process further comprises a third step offorming a film comprising the A-b-B di-block copolymer inside the atleast one trough. The lateral position of a line-forming micro-domain inthe trench is controlled by the distance between the at least one openend of the trough and the at least one edge of the mesa. The distance isabout 0.5P to about 1.0P, wherein the symbol P refers to the lamellardomain period of the A-b-B di-block copolymer. The edge pins one blockof the di-block copolymer. The process further comprises a fourth stepof assembling line-forming micro-domains of the di-block copolymerwithin the film. The micro-domains form self-assembled structures.Preferably, the micro-domain structures are nanostructures. Thestructures are oriented substantially normal to the first sidewall andsecond sidewall. The process comprises a fifth step of removing at leastone micro-domain from the film to obtain an oriented structure in thetrough. The oriented structure is substantially normal to the firstsidewall and the second sidewall, and substantially perpendicular to thesurface layer. The oriented structure comprises a pattern consistingessentially of an array of substantially parallel lines. The array ofsubstantially parallel lines has a sub-lithographic dimension.Preferably, the array of substantially parallel lines is a nanoarray.The oriented structure (nanoarray of substantially parallel lines) iscontrolled in both alignment and registration (lateral position withinthe trough).

The present invention relates to an oriented structure preparedaccording to the following process. The process comprises a first stepof providing a substrate having an energetically neutral surface layer.The energetically neutral surface layer comprises at least one mesaintegrally disposed thereon. The mesa has at least one edge. At leastone trough is integrally disposed on the mesa. The at least one troughcomprises a bottom surface, a substantially planar first sidewall and asubstantially planar second sidewall opposite the first sidewall. Thefirst sidewall and the second sidewall are substantially normal to thesurface layer. The first and second sidewalls are separated by adistance corresponding to the width of the bottom surface of the trough.The at least one trough has at least one open end. The process comprisesa second step of providing a linear substantially symmetrical A-b-Bdi-block copolymer. The process further comprises a third step offorming a film comprising the A-b-B di-block copolymer inside the atleast one trough. The lateral position of a line-forming micro-domain inthe trench is controlled by the distance between the at least one openend of the trough and the at least one edge of the mesa. The distance isabout 0.5P to about 1.0P, wherein P refers to the lamellar domain periodof the A-b-B di-block copolymer. The edge pins one block of the di-blockcopolymer. The process further comprises a fourth step of assemblingmicro-domains of the di-block copolymer within the film. Themicro-domains form self-assembled structures. Preferably, the structuresare nanostructures. The structures are oriented substantially normal tothe first sidewall and the second sidewall, and oriented substantiallyperpendicular to the surface layer. The process comprises a fifth stepof removing at least one micro-domain from the film to obtain anoriented structure in the trough. The structure is orientedsubstantially normal to the first sidewall and second sidewall, andsubstantially perpendicular to the surface layer. The oriented structurecomprises a pattern consisting essentially of an array of substantiallyparallel lines. The array of substantially parallel lines has asub-lithographic dimension. Preferably, the array of substantiallyparallel lines is a nanoarray. The oriented structure (nanoarray ofsubstantially parallel lines) is controlled in both alignment andregistration (lateral position within the trough).

Referring to FIG. 1, a first topographic laminate 1 is represented. Asubstrate 10 supports a first topographic “phase pinning” pattern 20 anda second topographic “guiding” pattern 30. The first topographic “phasepinning” pattern 20, having the morphology of a mesa or ledge, containsan edge 60. In FIG. 1, the edge 60 of the mesa is positioned at afunctional distance 5 from an open end of the trough. Preferably, thesubstrate 10 can be a material of the IUPAC group 11, 12, 13 and 14elements; plastic materials, silicon dioxide, glass fused silica, mica,ceramic, metals deposited on the aforementioned substrates, combinationsthereof and the like. Preferably, the distance between the open end ofthe trough in the second topographic pattern 30 and the edge 60 of themesa in the first topographic pattern 20 is about 0.5P to about 1.0P. Inan alternative embodiment, the substrate 10 can be a laminate. The firsttopographic “phase pinning” pattern 20 can be formed either beforeformation of the second topographic “guiding” pattern 30 or, in thealternative, after formation of the second topographic “guiding” pattern30. The first topographic pattern 20 can be formed by anyphotolithographic technique known to one of ordinary skill in the art. Aphotoresist is employed to produce the first topographic pattern 20. Thephotoresist material can be any material known to one of ordinary skillin the art. Preferably, the photoresist is a thermoplastic polymer orcopolymer that can be crosslinked by means of heat, UV light, visiblelight or the like. The second topographic pattern 30 comprises themorphology of a trough. As stated above, the trough is comprised of twosides 110, and a bottom surface 120. The two sidewalls 110 and thebottom surface 120 are made energetically neutral by a process known toone of ordinary skill in the art. The first topographic pattern 20 is“phase pinning” because a di-block copolymer (one that is able toself-assemble into lamellar micro-domains) can be “pinned” by an edge 60of the first topographic pattern 20. The edge 60 of the firsttopographic “phase pinning” pattern 20 is formed by a first topographicpattern 20 having the morphology of a mesa or ledge. In FIG. 1, the edge60 of the mesa is positioned at a functional distance 5 from an open endof the trough. The edge 60 can pin one of the blocks of a di-blockcopolymer (not shown). The “pinning” action performed by the firsttopographic pattern allows for controlled lateral placement of aself-assembling di-block copolymer. The controlled lateral placement isnot achieved in the prior art. Such control can be obtained usingpatterns of length scales accessible with optical lithography.

Referring to FIG. 2, a second topographic laminate 2 is represented. Asubstrate 10 supports a first topographic “phase pinning” pattern 20 anda second topographic “guiding” pattern 30. The first topographic “phasepinning” pattern 20, having the morphology of a mesa or ledge, containsan edge 60. In FIG. 2, the edge 60 of the mesa is positioned at afunctional distance 5 from an open end of the trough. The trough iscomprised of two sides 110 and a bottom surface 12. Preferably, thedistance 5 between the open end of the trough in the second topographicpattern 30 and the edge 60 of the mesa in the first topographic pattern20 is about 0.5P to about 1.0P. Preferably, the substrate 10 can be amaterial of the IUPAC group 11, 12, 13 and 14 elements; plasticmaterials, silicon dioxide, glass fused silica, mica, ceramic, metalsdeposited on the aforementioned substrates, combinations thereof and thelike. The substrate 10 can also be a laminate. The first topographic“phase pinning” pattern 20 can be formed either before formation of thesecond topographic “guiding” pattern 30 or, in the alternative, afterformation of the second topographic “guiding” pattern 30. A photoresistis employed to produce the first topographic pattern 20. The photoresistmaterial can be any material known to one of ordinary skill in the art.Preferably, the photoresist is a thermoplastic polymer or copolymer thatcan be crosslinked by means of heat, UV light, visible light or thelike. The second topographic pattern 30 comprises the morphology of atrough which is comprised of two sides 110, and a bottom surface 120.The first topographic pattern 20 is “phase pinning” because a di-blockcopolymer (one that is able to self-assemble into lamellarmicro-domains) can be “pinned” by an edge 60 of the first topographicpattern 20. The edge 60 of the first topographic phase pinning pattern20 is formed in a first topographic pattern 20 having the morphology ofa mesa or ledge. In FIG. 2, the edge 60 of the mesa is positioned at afunctional distance 5 from an open end of the trough. The bottom surface120 and the two sidewalls 110 of the trough are made energeticallyneutral. Once the trough is made energetically neutral, the surface ofthe first and second topographic pattern can be coated with aself-assembling di-block copolymer 220. The edge 60 can pin one of theblocks of the di-block copolymer 220. The di-block copolymer 220comprises alternating lamellae 230 and 240 formed by self-assembly ofthe two distinct blocks of the copolymer. One block of the di-blockcopolymer assembles to form lamellae 230 and the second block of thedi-block copolymer assembles to form lamellae 240. The “pinning” actionperformed by the first topographic pattern 20 allows for controlledlateral placement of a self-assembling di-block copolymer. Thecontrolled lateral placement (registration) is not achieved in the priorart. In the present invention, such control can be obtained usingpatterns of length scales accessible with optical lithography.

Referring to FIG. 3, a third topographic laminate 3 is represented. Asubstrate 10 supports a first topographic “phase pinning” pattern 20 anda second topographic “guiding” pattern 30. The first topographic “phasepinning” pattern 20, having the morphology of a mesa or ledge, containsan edge 60. In FIG. 3, the edge 60 of the mesa is positioned at afunctional distance 5 from an open end of a trough. The trough iscomprised of two sides 110 and a bottom surface 120. Preferably, thefunctional distance 5 between an open end of the trough in the secondtopographic pattern and the edge of the mesa in the first topographicpattern is about 0.5P to about 1.0P. Preferably, the substrate 10 can bea material of the IUPAC group 11, 12, 13 and 14 elements; plasticmaterials, silicon dioxide, glass fused silica, mica, ceramic, metalsdeposited on the aforementioned substrates, combinations thereof and thelike. The substrate 10 can also be a laminate. The first topographic“phase pinning” pattern 20 can be formed either before formation of thesecond topographic “guiding” pattern 30 or, in the alternative, afterformation of the second topographic “guiding” pattern 30. A photoresistis employed to produce the first topographic pattern 20. The photoresistmaterial can be any material known to one of ordinary skill in the art.Preferably, the photoresist is a thermoplastic polymer or copolymer thatcan be crosslinked by means of heat, UV light, visible light or thelike. The second topographic pattern 30 comprises a trough comprised oftwo sides 110, and a bottom surface 120. The first topographic pattern20 is “phase pinning” because a di-block copolymer (one that is able toself-assemble into lamellar micro-domains) can be “pinned” by an edge 60of the first topographic pattern 20. The edge 60 of the firsttopographic “phase pinning” pattern 20 is formed in a first topographicpattern 20 having the morphology of a mesa or ledge. In FIG. 3, the edge60 of the mesa is positioned at a functional distance 5 from an open endof the trough. The bottom surface 120 and the two sidewalls 110 of thetrough are made energetically neutral. Once the trough is madeenergetically neutral, the surface of the first and second topographicpattern can be coated with a film of a self-assembling di-blockcopolymer 220 (See FIG. 2). Preferably, an annealing step is performedon the film to obtain equilibrium morphology. The edge 60 can pin one ofthe blocks of the di-block copolymer. The “pinning” action performed bythe first topographic pattern 20 allows for controlled lateral placementof a self-assembling di-block copolymer. The controlled lateralplacement is not achieved in the prior art. In the present invention,such control can be obtained using patterns of length scales accessiblewith optical lithography. One type of block of the di-block copolymer isthen removed by methods known to one of ordinary skill in the art. Afterremoval of blocks 240 (See FIG. 2), only blocks 230 remain. A pattern ofalternating lines and spaces is thus obtained. The pattern can beemployed as a mask to etch the underlying substrate.

Referring to FIG. 4, a plan-view scanning electron microscope (SEM)micrograph of lamellar micro-domains of apolystyrene-b-polymethylmethacrylate (PS-b-PMMA) di-block copolymerdeposited on the top of a topographic laminate is depicted. Thepolystyrene-b-polymethylmethacrylate di-block copolymer was coated as afilm on a topographic laminate. In particular, the coating solutioncomprised 38 kg/mol PS and 36.8 kg/mol PMMA. The edge 60 of the mesapins one phase of micro-domains while sidewall 110 aligns the lamellarmicro-domains perpendicular to the sidewall surface.

The present invention, in one embodiment, relates to a method forpreparing a polymer structure consisting essentially of self assembledlamellar microdomains. The polymer structure has a sub-lithographicdimension. The method comprises the following steps. A substrate havingan energetically neutral surface layer is obtained. The energeticallyneutral surface layer comprises a first topographic “phase pinning”pattern and a second topographic “guiding” pattern. The firsttopographic “phase pinning” pattern comprises a mesa having an edge. Thesecond topographic “guiding” pattern comprises a trough. The trough hasat least one open end. The trough cannot be closed off like a boxstructure. The distance between the at least one open end of the troughand the edge of the mesa is about 0.5P to about 1.0P. The symbol Prefers to the lamellar domain period of a di-block copolymer.

The method further comprises a step of obtaining a self-assemblingdi-block copolymer. The self-assembling di-block copolymer is thencoated on the energetically neutral surface. The edge of the mesa pinsone block of the di-block copolymer. A coated substrate is obtained.

The method further comprises a step of annealing the coated substrate toobtain self-assembled micro-domains of the di-block copolymer; whereinthe microdomains are controlled in both alignment and registration(lateral position within the trough). A polymer structure consistingessentially of self assembled lamellar microdomains is thus obtained.

One type of block of the self-assembled lamellar micro-domains is thenremoved as by etching or the like. A pattern of alternating lines andspaces is thereby obtained. Such a pattern can be employed as a mask toetch the underlying substrate. The width of the lines can be about 10 nmto about 100 nm.

While the invention has been described by specific examples andembodiments, there is no intent to limit the inventive concept except asset forth in the following claims.

1. A method for preparing a polymer structure consisting essentially oflamellar micro-domains, the polymer structure having a sub-lithographicdimension, the method comprising: obtaining a substrate having anenergetically neutral surface layer, the energetically neutral surfacelayer comprising a first topographic “phase pinning” pattern and asecond topographic “guiding” pattern; the first topographic “phasepinning” pattern comprising a mesa having an edge; the secondtopographic “guiding” pattern comprising a trough, the trough having atleast one open end; wherein the distance between the at least one openend of the trough and the edge of the mesa is about 0.5P to about 1.0P,and wherein P refers to the lamellar domain period of a di-blockcopolymer; obtaining a self-assembling di-block copolymer; coating theself-assembling di-block copolymer on the energetically neutral surfaceto obtain a coated substrate, wherein the edge pins one block of thedi-block copolymer; and annealing the coated substrate to obtainmicro-domains of the di-block copolymer; wherein the micro-domains arecontrolled in both alignment and registration (lateral position in thetrough).